Apparatus for detecting and identifying the existence of buried or submerged objects are known in the prior art. For example, U.S. Pat. No. 4,641,566 to Pomeroy discloses a process for locating buried plastic mines or nonmetallic objects which involves spraying a suspected area with a leach of ionized metal and leaching the ionized metal into the soil to leave a metallic concentrate on an impervious object, such as a plastic mine. An array of detectors detects anomalies of concentrations of the metal, the concentrations being the result of the leach settling on or about the impervious object.
U.S. Pat. No. 5,452,639 to Aulenbacher et al. discloses ground-scanning sensors mounted on a light-weight, unmanned, remote-controlled vehicle which travels over areas contaminated with buried ammunition to automatically locate and map the area without endangering the searching crew. The controlled vehicle is controlled from, and the sensor signals are evaluated in, a second vehicle which is generally disposed in the immediate vicinity of the area being examined.
U.S. Pat. No. 5,869,967 to Strauss discloses a device for the detection of objects lying in the earth which, irrespective of topography, soil structure, and state of the terrain, permits high surface yields with great precision in identifying the position of the objects to be detected without endangering the operating personnel. In particular, the device comprises at least one jib mounted on a mobile device which is swivellable about a vertical axis on whose free end are arranged adjacent to one another several measuring heads for sweeping over strip-shaped surface areas of the terrain to be investigated. With the measuring heads on the free end of the jib, at least one ground marking device is arranged for distinguishing the find site determined by the measuring heads. The ground marking device includes a paint spraying device as well as a stake marking device next to aerial measuring head.
Problems associated with these prior systems include their inability to hover at a predetermined height without being anchored or tethered. While submarines are capable of fixed depth operations, such vehicles use pumps or vertical thrusters to achieve buoyancy. Some known devices, which use gas filled flexible chambers to control buoyancy and therefore the depth of vehicle operation, are prohibitively expensive due to the supply of gas which must be carried in the vehicle for correction of depth errors over a sustained period of vehicle operation.